A year ago, General Dynamics-NASSCO didn't have any firm orders to build commercial tankers, one of the San Diego company's specialties. Today, it has seven.

The resurgence continued Tuesday when Seabulk Tankers (SEACOR) hired NASSCO to build a 610-foot product carrier at an undisclosed price.

The order could further stoke job growth at NASSCO, which is moving from a 20-year low of 3,000 workers to roughly 4,100 employees. The boom has been partly fueled by SEACOR, which ordered two tankers in September. That built on the momentum NASSCO began generating last May when American Petroleum Tankers ordered four vessels. More work may be coming: SEACOR said it has taken an option for another tanker.

" Although we don’t anticipate increasing the number (of workers) previously reported, the addition of this contract will sustain employment for a longer period of time," said Sarah Strang, a spokeswoman for NASSCO.

NASSCO President Fred Harris has said the boom represents a delayed reaction to the end of the recession. Maritime analysts said the pickup also stems from shipping companies' need to replace older vessels with new ones that are more fuel-efficient and environmentally friendly. NASSCO referred to that trend in a news release Tuesday, saying: "This new 610-foot-long tanker is a continuation of the ECO MR tanker design, which delivers improved fuel efficiency and incorporates the latest environmental protection features, including a Ballast Water Treatment System."

In the same news release, NASSCO General Manager Kevin Graney said: “NASSCO remains committed to bringing the most economical and environmentally sound technology to Jones Act owners and operators. We are very pleased to extend our partnership with SEACOR through a third and potentially a fourth ECO tanker. This follow-on order is a clear indication that NASSCO is the shipyard of choice for Jones Act tankers.”

The Jones Act is an historic piece of federal maritime legislation that improved health, safety and employment conditions for merchant marines. LegalMatch.com said the act also "requires ships traveling between United States ports to be constructed by United States companies and owned by a United States company or citizen. Members of the ships’ crews must be United States citizens or legal aliens."

The new SEACOR contract comes as NASSCO is bustling with construction and repair work for the Navy.

Last week, the company laid the keel of of the USNS Lewis B. Puller, a mobile landing platform ship that the Navy and Marines will use as a staging area at sea. NASSCO also built the first two MLPs. The work has so far earned the company more than $1 billion.

NASSCO also is currently performing repairs and upgrades on the littoral combat ship Independence.

Next door, BAE San Diego Ship Repair is doing work on the destroyers Russell and Benford and the amphibious warships Rushmore and Green Bay.